Fuel Additive Training

Cost Factor in Oil Fired Plant

Fireside Concerns of Solid and Liquid Firing

Preburner corrosion/fouling Burner corrosion/fouling Furnace slagging High temperature corrosion Cold end corrosion Gaseous emissions Poor combustion

nozzle pluggage tank corrosion sludge in oil (asphaltenes) water in oil MB growth

Minimizing Preburner and Burner Fouling:

Adding dispersants to fuel to minimize fouling Dispersants promote a homogeneous fuel mixture Improves suspension of Asphaltenes and solids

Preburner and Burner Fouling- MFO Case:

FUEL INJECTION SPRAY PATTERNS

Furnace Slagging Concerns of solid & Liquid Firing

Poor heat transfer

Gas path pluggage

Fireside damage

Inhibit ash removal

Typical Location of Fouling and Slagging in Coal Fired Boiler

Major Slagging Elements

Vanadium Sodium Nickel Potassium Calcium Lead Zinc Iron

Oxidized Element Melting Temperature

K2O 662 F

K2O2 914 F

KO2 716 F

Na2O2 860 F

V2O5 1247 F

PbO 1626 F

PbO2 554 F

P2O3 74.8 F

CHEMICAL NATURE OF PROBLEM (cont)

Alkali oxides of Na & K adhere to metal surfaces through reaction with SO3

S (usually present as iron pyrites) converted to SO2 SO2 + ½ O2 -> SO3 Na2O + SO3 -> Na2SO4 3 SO3 + 3 Na2SO4 + Fe2O3 -> 2 Na3Fe(SO4)3

Ash constituents adhere to molten film building in thickness

Minimizing Slagging in Furnace Mechanically

- retrofit boiler to burn different fuel

- tune burner guns

- tune grate speed

- check for proper soot blower alignment Operationally

- change fuel

- change load/firing rate

- increase excess air

- increase soot blow frequency

Minimizing Slagging in Furnace Chemically

Elevate melting point of impurities in fuel Increase friability of slag Promote passivation of boiler surfaces

Additive Melting Temperature Magnesium oxide 3180 oF Calcined Alumina 3875 oF Calcium Silicate 3255 oF Aluminum oxide 5166 oF Titanium oxide 3659 oF

How Fuel Additive Works: Fuel additives function by elevating the

melting point of the compounds formed by the impurities in the fuel

The goal is to minimize the amount of sticky, slag forming material in the flue gas

If the compounds formed remain dry, they are more likely to fall out the bottom as ash or be collected in the precipitators.

Melting Temperature of Compounds after Treatment

COMPOUND MELTING TEMPERATURES

3MgO * V2O5 2175 F

NaO * AlO3 2875 F

NiO * Al2O3 3362 F

Al2O3 * Na2O * 6SiO2 2010 F

K2 * Al2O3 * SiO3 1800 F

K2O * Al2O3 2SiO2 * Al2O3 3056 F

K2O * Al2O3 4SiO2 * Al2O3 2890 F

K2O * Fe2O3 * 4SiO2 2875 F

2K * AlSi2O6 * Mg2SO 2825 F

K2SO4 * MgO 1953 F

K2O * MgO * SiO2 1750 F

Typical MFO Analysis

Typical Coal Analysis

COMBUSTION

Combustion is the breakdown of the organics to a gas during the slow chemical reaction of oxidation Coal combustion &/or fouling problems determined by :

Combustion Reactions

Generic Reaction

HC Fuel + O2 CO2 + H2O + SOx + NO x + Heat

Specific Reaction: HC (BTU/lb) C + O2 CO2 14,100 CO + ½O2 CO2 3,960 H2 + O2 H2O + ½O2 61,100 S + O2 SO2 3,980

Poor Combustion Concerns

Smoking stack

High carbon in ash (LOI)

Increased fuel usage

Particulate emissions

Poor boiler efficiency

Combustion Catalyst

improves boiler efficiency

reduces volume of ash produced

reduces carbon content in ash

reduces particulate in flue gas

lowers excess air requirements (lowering NOx and

COMBUSTION IMPROVEMENT

Continuous application of combustion catalyst Reduced activation energy to accelerate

combustion Reduced carbon content in fly ash Reduced % excess air requirement

FUEL + AIR

FREE RADICALS

EACT1

Progress of Reaction

EACT2

Pot

enti

al E

nerg

y

HEAT OF COMBUSTION FLUE GAS

POTENTIAL ENERGY DIAGRAM FOR COMBUSTION REACTIONS

HOT END PROBLEMS

Hot Section defined as operating temperature > 1000 F (535 C) Furnace, convective zone, superheaters

Low viscosity ash formation Slag deposits Metal surface corrosion

FURNACE SLAG DEPOSITS

Untreated vs Treated Slagging1000x SEM

Highlighted area #2 -Treated:

• Larger pores

• Weaker and lighter deposits

• Easier to remove

Highlighted area #1- Untreated:

• Small pores and packed

• Hard and tenacious deposits

• Create problems

COLD END PROBLEMS

Cold section defined as operating temperature < 1000 F (535 C) Air preheaters, ID fans, economisers, boiler

stack

Caused by sulphuric acid attack formed when flue gas cooled below the acid dew point

Metal sulphates formed result in fouling

Minimizing Cold End Corrosion Can be minimized by adding magnesium and/or

magnesium oxide to the fuel at the time of combustion.

The magnesium reacts with the sulfur to reduce the concentration of SO3 compounds in the flue gas.

Reducing the amount of sulfur available to form sulfur dioxide compounds which result in the formation of H2SO4

By minimizing the amount of sulfuric acid present in the flue gas, the magnesium oxide effectively elevates the acid dew point of the sulfuric acid that does form.

Neutralization Reaction

Mg + 2O2 + S MgSO4

MgO + 3/2O2 + S MgSO4

Mg + 1/2O2 MgO

Mg + Cl MgCl

Treatment Strategies

TREATMENT STRATEGIES

Neutralisation Alkaline additive to neutralise sulphuric acid

as formed

Catalyst Deactivation Coating &/or reaction with catalysts (Cu, Fe)

Continuous application to coal prior to pulverisers

Often combined treatment with combustion catalyst

FIRESIDE ADDITIVES

Raises fusion temperature of adherent deposits Produces dry, friable, high mp compound Weakens bonding of slag to metal surface

Reacts with complex sulphates & other slag components Changes slag from a hard, dense material to

soft, expanded, porous powder

Forms metallic film on metal surface Protects surfaces from corrosive action Minimises catalytic action of SO2 to SO3

Diffusion of Additive Throughout Slag Materials

Particle size of additive (MgO) in fireside gas is 0.3 – 0.03

The combustion gas diffuses throughout slag due to permeability of slag materials

This mechanism keeps the slag formed is lighter, softer, and easier to remove via shootblowing

Treatment Results

Treatment Results

Fly Ash pH

• The easiest means to measure the efficacy of chemical treatment

• Sample taken from Air Heater outlet

• pH checking thru 1% slurry of fly ash (fly ash + demin water)

• Target fly ash pH: 6.5 - 8.5

IMPROVING COMBUSTION EFFICIENCY

AMERGY 5800 Plus ® Combustion Catalyst Data

0

2

4

6

8

10

12

14

16

April 14, 2002 April 24, 2002 May 4, 2002 May 14, 2002 May 24, 2002 J une 3, 2002

% O

xyge

n Rea

ding

(Blu

e)%

CO2 R

eadi

ng (R

ed)

Amergy 5800Plus ® Feed Initiated

% CO2 Curve

% Oxygen Curve

ACID DEWPOINT & TEMPERATURE RELATIONSHIPS

Fuel Additive Products

Powder Products FST 5370

• Slag inhibitor with corrosion inhibitor Drew 11-GFM

• Slag inhibitor & combustion catalyst Drew 11-GFS

• Slag inhibitor ~ dosage 0.1 kg/Ton fuel

Liquid Product: Amergy 222N for MFO preburner ~ dosage 0.15 – 0.25 kg/Ton fuel

Questions?